The development of minimally invasive and non-invasive surgical techniques have remained a prime research focus in the bio-medical area over the past two decades due to several advantages over conventional surgery methods. Computer-assisted surgery and medical robotics have improved the ways in which surgery has been done in the past. In image-guided surgery, the pre-operative planning scheme is executed using medical images/data, such as CT, MRI, X-Ray or Ultrasound images, gathered prior to the intervention. This information helps the surgeons in simulating, visualizing, guiding and assisting a surgical procedure (1-6).
The applications of robots and computer integration in medicine range from simplistic laboratory robots for tool positioning to highly complex surgical robots that carry out surgical procedures under computer control. Most of the robotic systems for surgery aim at assisting in minimally invasive surgical procedures. One such surgical robot is the da Vinci® surgical system, which has successfully completed hundreds of cardiac, general and other types of procedures. Other notable examples are the AESOP and ZEUS robotic surgical systems.
There are various non-invasive alternatives to various surgical indications, such as microwave, RF, lasers, X-rays, or nuclear radiation exposure, however, a safer and radiation-free modality, known as High Intensity Focused Ultrasound (HIFU) is gaining importance and has shown high potential for treatment of a wide range of medical conditions (7-14). HIFU is a non-invasive technique capable of selective destruction of tissue volumes within the body. HIFU works by producing damage in the focal region of an acoustic beam in a predictable and reproducible manner, while sparing overlying tissue. Studies have shown that cancers/tumors are relatively more receptive to heat and the range of temperatures induced by HIFU has been shown to achieve high localized cytotoxicity. This is a phenomenon that does not occur with microwave or infrared exposure.
The use of ultrasound as a modality for diagnostic imaging in medicine has been well known for more than two decades. Its therapeutic applications, for example in sports medicine (micro-massaging action), cancer treatment (hyperthermia), enhanced chemotherapy (e.g. breach of blood brain barrier by focusing ultrasound to a discrete point), stone disintegration (shock-wave therapy), or tissue ablation (Focal Ultrasound Surgery), opened up a big potential for a wide variety of medical applications. Therapeutic ultrasound is established in the treatment of diverse surgical conditions, such as cataract, liver cancer, and stones, without danger to healthy tissue. The unique properties of ultrasound to be able to achieve tight focus at a given depth and non-invasively target localized tissue structures present significant treatment potential.
Several commercial devices that employ HIFU are available for treating prostate diseases. One such commercial HIFU system is the Sonablate 200™ (Focal Surgery Inc. Milpitas, Calif.), developed in 1992, for the treatment of a common prostate disease, Benign Prostatic Hyperplasia (BPH). In the Sonablate system, a 4-MHz transducer is used for both lesion induction and imaging purposes. Clinical trials of this machine were conducted in Japan and Europe. The device has undergone several modifications since then. Another commercial HIFU system called Ablatherm™ (Technomed International, Lyon, France) utilizes separate transducers, 7.5 MHz for imaging and 2.25 MHz for therapy purposes. This system is also targeted for BPH treatment. Another version of this system called Ablatherm® (EDAP TMS S.A., France) is commercially available for treatment of BPH and prostate cancers.
All of the above mentioned prostate treatment systems are primarily targeted for BPH treatment with only a small percentage of success in prostate cancers without the aid of any adjuvant modality. One reason for the latter could be the preferentially high absorption in the rectal wall, thus allowing less energy to transfer deeper in the tissue. An Israeli company named Insightec, Ltd. has commercialized an image guided non-invasive HIFU surgery system for applications in soft tissues. This system for breast surgery relies on expensive MRI guidance.
One system which has been designed for breast cancer is described in International Publication WO03/059434 published on Jul. 24, 2003. This arrangement utilizes a robotic manipulator which carries a jig assembly including an array of treatment probes and a single diagnostic probe. The probes can be moved by the robotic manipulator in x, y and Θ directions. The diagnostic probe first determines the size of the tumor and the treatment probes are then used to ablate the tumor by the superposition of ultrasonic waves at a con-focal region.